Intake and exhaust cylinder valves have been used in internal combustion engines from their very beginning. Various types of valves have been used in the past including poppet, reed, sliding-sleeve, and rotary types. Typically, a modern four-stroke internal combustion engine uses poppet valves and a two-stroke internal combustion engine uses reed valves. Poppet valves are operated by different types of valve trains and reed valves are operated by air pressure.
The most typical modern four-stroke engine has two intake and two exhaust valves located inside each cylinder head and operated by two parallel camshafts (DOHC). The camshafts are driven from the crankshaft by sprockets and chain or toothed belt. The camshaft sprocket is twice as large as the crankshaft sprocket which causes the camshaft to turn at half the speed of the crankshaft. Thus, every two revolutions of the crankshaft produce one revolution of the camshaft. The camshaft has one or more camshaft lobes which press against cam followers. The cam followers can be either hydraulic or mechanical.
Because of the significant advantages regarding valve operation and maintenance, most modern engines use hydraulic cam followers (lifters) which provide smooth and quiet self-adjusting operation. The shape of the cam lobes determines the valve's timing, duration, and lift. The valve's timing, duration, and lift are critical for engine performance because they determine engine breathing. Therefore, different shapes of cam lobes are required for engines with different operating speeds. Since the shape of cam lobes can not be changed during engine operation, it does not allow adjustment to achieve optimal engine performance during engine operation. A recent development provides two different camshafts which operate the same valves according to different requirements, i.e., the first camshaft operates the valves at low operating speeds and the second camshaft operates the same valves at high operating speeds. This provides better engine operation and decrease exhaust pollution.
In any case valve operation requires a complicated and expensive mechanical configuration which has a negative effect on engine volume and increases manufacturing costs.
Therefore, it is an object of the present invention to provide a device which will enable optimal engine performance, significantly simplify valve train configuration and, consequently, significantly decrease manufacturing costs and engine volume.